Alkaline cell with flat housing

Abstract

An alkaline cell having a flat housing, preferably of cuboid shape. The cell can have an anode comprising zinc and a cathode comprising MnO 2 . The housing can have a relatively small overall thickness, typically between about 5 and 10 mm. Cell contents can be supplied through an open end in the housing and an end cap assembly inserted therein to seal the cell. The end cap assembly includes a vent mechanism which can activate, when gas pressure within the cell reaches a threshold level typically between about 100 and 300 psig (6.89×10 5 and 20.69×10 5 pascal gage). The cell can have primary and supplemental vent mechanisms such as welded or thinned regions on the surface of the housing which may activate at different pressure levels. The cathode can be formed of a plurality of stacked slabs having aligned hollow centers with an elongated opening for anode material to be inserted therein.

1. A primary alkaline cell comprising a negative and a positive terminal, and an outer housing having a pair of opposing flat sides running along a portion of the length of said housing; said housing having a closed end and opposing open end and said housing not having any integral cylindrical sections; said cell further comprising an anode comprising zinc and a cathode comprising MnO 2  within said housing, a separator between said anode and cathode, and an end cap assembly sealing the open end of said housing;
 wherein the cathode comprises at least one cathode slab having an opening defined therethrough devoid of cathode material, with at least a portion of the outer surface of said cathode contacting the inside surface of said housing, 
 said end cap assembly sealing the open end of said housing thereby forming a boundary surface around the cell interior; 
 wherein the cathode comprises a plurality of rectangular shaped cathode slabs; wherein each of said slabs has a central opening devoid of cathode material; wherein said cathode slabs are stacked within the housing along the cell's central longitudinal axis so that said openings devoid of cathode material form a central core along said longitudinal axis, with the outer surface of said cathode contacting the inside surface of said housing; 
 wherein said cell comprises a vent mechanism located on said the boundary surface, wherein said vent mechanism activates to release gas pressure from within the cell as said gas pressure rises, said vent mechanism comprising a first and a second rupture zone on said boundary surface, wherein at least one of said rupture zones forms a groove on said boundary surface and the second rupture zone forms a weld on said boundary surface, wherein said rupture zones have the property that the first zone ruptures when gas pressure within the cell rises to a first pressure level and said second zone ruptures when gas pressure within the cell rises to a second pressure level being higher than said first pressure level allowing gas from within the cell to escape from the cell interior through said ruptures. 
 
     
     
       2. The cell of  claim 1  wherein said groove on said boundary surface defines a region thinner than the average thickness of said boundary surface. 
     
     
       3. The cell of  claim 1  wherein said first and second rupture zones are spaced apart on said boundary surface. 
     
     
       4. The cell of  claim 2  wherein the first rupture zone forms a groove on said boundary surface, said groove defining an area thinner than the average thickness of said boundary surface; and the second rupture zone is formed by a laser weld with within a portion of said boundary surface. 
     
     
       5. The cell of  claim 2  wherein said groove is formed by stamping said boundary surface. 
     
     
       6. The cell of  claim 1  wherein each of said rupture zones forms a groove on said boundary surface, said grooves each defining a region thinner than the average thickness of said boundary surface. 
     
     
       7. The cell of  claim 1  wherein the first zone on said boundary surface ruptures when gas pressure within the cell interior reaches a pressure level between about 250 and 800 psig (1724×10 3  and 5515×10 3  pascal gage) and said second zone on said boundary surface ruptures when gas pressure within the cell interior reaches a pressure level between about 800 and 2500 psig (5515×10 3  and 17235×10 3  pascal gage). 
     
     
       8. The cell of  claim 1  wherein the first rupture zone is formed by a groove on the outside surface of said housing and the second rupture zone is formed by a laser weld between the edge of a metal member and the inside surface of said housing thereby fixing said metal member along a portion of its edge to the inside surface of said outer housing in proximity to the open end of said housing. 
     
     
       9. The cell of  claim 8  wherein said metal member is a rectangular plate. 
     
     
       10. The cell of  claim 8  wherein said groove runs parallel to the closed end of the cell. 
     
     
       11. The cell of  claim 8  wherein the first zone on said boundary surface ruptures when gas pressure within the cell interior reaches a pressure level between about 250 and 800 psig (1724×10 3  and 5515×10 3  pascal gage) and said second zone on said boundary surface ruptures when gas pressure within the cell interior reaches a pressure level between about 800 and 2500 psig (5515×10 3  and 1724×10 3  pascal gage). 
     
     
       12. The alkaline cell of  claim 11  wherein the housing comprises metal having a wall thickness of between about 0.30 mm and 0.50 mm. 
     
     
       13. The alkaline cell of  claim 11  wherein said cell has an overall thickness of between about 5 and 10 mm, wherein said overall thickness is defined as the distance between the outside surface of opposing sides of said housing defining the short dimension of said housing.